The invention relates to a superconductor premixture prepared for fusion processing, a method for the production thereof, and a YBa.sub.2 Cu.sub.3 O.sub.7-x powder which can be used in preparing the premixture.
YBa.sub.2 Cu.sub.3 O.sub.7-x powder (x=0 to 0.5) is used for the preparation of technical superconductors. The powder is advantageously mixed with stabilizing additives which form sticking or pinning centers. The resulting premixture is pressed into compacts and heat treated, preferably by fusion processing. In fusion processing the surfaces of the powder particles of the premixture are heat-softened, so that in the cooling that follows the particles are bonded tightly to one another. The flow of the electric current through the grain boundaries is thus improved. The stabilizing additives usually have the effect of reducing the melting temperature of the premixture, so that the softening of the bodies that are to formed and the escape of molten material otherwise observed at higher fusion texturizing temperatures, can be prevented. The additives, which form sticking or pinning centers, permit increasing the critical current density in the superconductors. The pinning centers provide for an anchoring of the magnetic lines of flux, so that high critical currents can also be achieved in the magnetic field. Flux pinning additives for superconductors composes of copper oxide are disclosed, for example, in European Patent Applications EP-A-0 292 126 and 296 380.
The bodies obtained by fusion processing from high-temperature superconductor material can be used, for example, in the manufacture of electric motors and in the production of the so-called "flywheel." The flywheel rotates under superconducting conditions in the magnetic field and serves to store kinetic energy.